1. Field of the Invention
The present invention relates to a display, and more particularly to a display device and a driving method thereof. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for minimizing motion blurring and brightness deterioration in a display of motion pictures.
2. Description of the Related Art
In signal holding type display devices, such as liquid crystal display (LCD) device or an organic light emitting diode (OLED), a blurring phenomenon occurs on display screen when a motion picture is displayed. FIG. 1 is a diagram representing light emission characteristics of a cathode ray tube, FIG. 2 is a diagram representing light emission characteristics of a liquid crystal display device. The blurring phenomenon will be explained in conjunction with FIG. 1 that shows characteristics of a cathode ray tube (CRT), which is a signal impulse device and FIG. 2 that shows characteristics of an LCD device, which is a signal hold device.
As shown in FIG. 1, the CRT is a signal impulse type display device which displays data by making a phosphorus emit light for a very short time in an early stage of one field period such that most of the one frame period is a pause interval. Accordingly, a perceived image of an observer in a motion picture is clearly displayed in the CRT. In comparison, the liquid crystal display device, as shown in FIG. 2, data is supplied to a liquid crystal cell during a scanning period when a scan high voltage Vgh is supplied and then the data is maintained in the liquid crystal cell during a non-scanning period, which is most of one frame period. Thus, an incorrect perceived image of the displayed motion picture occurs because of the maintenance characteristic of the liquid crystal in the liquid crystal display device. The incorrect perceived image results is due to an integration effect of the displayed motion picture image that temporarily lasts in observer's eyes after a movement. Accordingly, even though the response speed of the liquid crystal display device is fast, an observer sees a blurred screen because of discordance between the movement detected by the eye and the static image of each frame.
FIG. 3 is a diagram representing the related art method of improving motion blurring by insertion of black data. To reduce the appearance of motion blurring in the liquid crystal display device of the related art, a method of reducing the holding time by inserting black data in a frame period has been used, as shown in FIG. 3. Thus, a method of reducing the holding time by inserting black data has characteristics similar to those of the CRT.
FIG. 4 is a diagram representing a data alignment of a normal state without inserting black data, and FIG. 5 is a diagram representing a data alignment where black data are inserted into the whole gray level area. As shown in FIG. 4, frame data is supplied to a liquid cell throughout one frame. The related art method of improving motion reduces the holding time D1˜D5 of frame data within each frame and inserts black data B1˜B5, as shown in FIG. 5, thereby driving a liquid crystal display device by a pseudo-impulse scheme to reduce the motion blurring phenomenon. Accordingly, as shown in FIG. 3, the gray level of the input data is provided for about 60% of each frame and the inserted black level is expressed for about 40% of each frame.
FIG. 6 is a graph of a display brightness using the normal state supplying method and the display brightness using the black data insertion supplying method. The motion blurring problem can be solved to a certain extent by the pseudo-impulse method shown in FIGS. 3 and 5. However, the data holding time D1˜D5 of each frame is reduced while the black data are inserted such that the brightness BDI of the display is decreased, as shown in FIG. 6.